With a single punch, Trayvon Martin decked the Neighborhood Watch volunteer who eventually shot and killed the unarmed 17-year-old, then Trayvon climbed on top of George Zimmerman and slammed his head into the sidewalk, leaving him bloody and battered, law-enforcement authorities told the Orlando Sentinel.

That is the account Zimmerman gave police, and much of it has been corroborated by witnesses, authorities say. There have been no reports that a witness saw the initial punch Zimmerman told police about.

Zimmerman has not spoken publicly about what happened Feb. 26. But that night, and in later meetings, he described and re-enacted for police what he says took place.

In his version of events, Zimmerman had turned around and was walking back to his SUV when Trayvon approached him from behind, the two exchanged words and then Trayvon punched him in the nose, sending him to the ground, and began beating him.

Zimmerman told police he shot the teenager in self-defense.

Civil-rights leaders and more than a million other people have demanded Zimmerman's arrest, calling Trayvon a victim of racial profiling and suggesting Zimmerman is a vigilante.

Trayvon was an unarmed black teenager who had committed no crime, they say, who was gunned down while walking back from a 7-Eleven with nothing more sinister than a package of Skittles and can of Arizona iced tea.

Zimmerman's account

This is what the Sentinel has learned about Zimmerman's account to investigators:

He said he was on his way to the grocery store when he spotted Trayvon walking through his gated community.

Trayvon was visiting his father's fiancée, who lived there. He had been suspended from school in Miami after being found with an empty marijuana baggie. Miami schools have a zero-tolerance policy for drug possession.

Police have been reluctant to provide details about their evidence.

But after the Sentinel story appeared online Monday morning, City Manager Norton Bonaparte Jr. issued a news release, saying there would be an internal-affairs investigation into the source of the leak and, if identified, the person or people involved would be disciplined.

He did not challenge the accuracy of the information.

At a Monday news conference, Trayvon's mother, father and their lawyers called the report that their son was suspended from school because of a marijuana baggie irrelevant and needlessly hurtful.

Trayvon's father, Tracy Martin, said "even in death, they are still disrespecting my son, and I feel that that's a sin."

Supporters have held rallies in Sanford, Miami, New York and Tallahassee, calling the case a tragic miscarriage of justice.

Civil-rights activist the Rev. Al Sharptonheadlined a rally in Sanford on Thursday that drew an estimated 8,000 people. The Rev. Jesse Jacksonon Sunday spoke at an Eatonville church, where he called Trayvon a martyr.

Zimmerman has gone into hiding. A fringe group, the New Black Panther Party, has offered a $10,000 reward for his "capture."

One-minute gap

On Feb. 26, when Zimmerman first spotted Trayvon, he called police and reported a suspicious person, describing Trayvon as black, acting strangely and perhaps on drugs.

Zimmerman got out of his SUV to follow Trayvon on foot. When a dispatch employee asked Zimmerman if he was following the 17-year-old, Zimmerman said yes. The dispatcher told Zimmerman he did not need to do that.

There is about a one-minute gap during which police say they're not sure what happened.

Zimmerman told them he lost sight of Trayvon and was walking back to his SUV when Trayvon approached him from the left rear, and they exchanged words.

Trayvon asked Zimmerman if he had a problem. Zimmerman said no and reached for his cell phone, he told police. Trayvon then said, "Well, you do now" or something similar and punched Zimmerman in the nose, according to the account he gave police.

Zimmerman fell to the ground and Trayvon got on top of him and began slamming his head into the sidewalk, he told police.

Zimmerman began yelling for help.

Several witnesses heard those cries, and there has been a dispute about whether they came from Zimmerman or Trayvon.

Lawyers for Trayvon's family say it was Trayvon, but police say their evidence indicates it was Zimmerman.

One witness, who has since talked to local television news reporters, told police he saw Zimmerman on the ground with Trayvon on top, pounding him — and was unequivocal that it was Zimmerman who was crying for help.

Zimmerman then shot Trayvon once in the chest at very close range, according to authorities.

When police arrived less than two minutes later, Zimmerman was bleeding from the nose, had a swollen lip and had bloody lacerations to the back of his head.

Paramedics gave him first aid but he said he did not need to go to the hospital. He got medical care the next day.

The Department of Justice last week opened a civil-rights investigation into what happened, and Gov. Rick Scott appointed a special prosecutor, Angela Corey, the state attorney for Duval, Clay and Nassau counties.

In an interview with the Sentinel on Monday, she said it is too early to say whether she would leave it to a Seminole County grand jury, which local prosecutors had decided to convene April 10, to decide whether to charge Zimmerman with manslaughter or some other crime.

Her two-lawyer team worked through the weekend on the case, she said, and it will take several more days, perhaps a week, to decide how best to proceed.

She would not comment about any specific pieces of evidence, including what authorities have learned from a 16-year-old Miami girl who may have been on the phone with Trayvon as he and Zimmerman came face to face.

Benjamin Crump, one of the family's attorneys, told reporters last week that the girl told him she heard the two exchange words then a sound that she believed was Zimmerman pushing Trayvon.

Corey said her office has routinely challenged self-defense claims and will pursue charges in this case if the evidence supports it.

One month after the shooting death of Trayvon Martin, nearly three out of four Americans say police should arrest the Neighborhood Watch volunteer who pulled the trigger, according to a new national survey.